将文本框内容转化换位double类型使用convert.Todouble（）
A. 对
B. 错
What does a DSC control unit do when a DSC message is received?
A. When receiving DSC messages other than a distress, urgency and safety call, the control unit is able to provide for an automatic transmission acknowledging the call received.
B. The information contained in the DSC message is decoded and displayed on the from panel.
C. The information may be stored in an internal memory.
D. All of the above.
Which frequency is used for inter-ship DSC calling purposes?
A. 2. 177 kHz.
Both 2, 177 kHz and 156, 525 MHz.
C. 156. 525 MHz.
D. 2, 177 kHz and 2, 189. 5 kHz used in pairs.
What is the emission designation for VHF-FM voice in the maritime service?
A. F3C.
B. J2B.
C. G3E.
D. J1B.
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